The present invention relates to membrane separation cells for separating a permeate from a feed solution. The invention is particularly useful as a reverse-osmosis cell in an artificial kidney, especially the portable type, and therefore is described below with respect to such an application, but it will be appreciated that the invention could be used in many other applications, for example as reverse-osmosis cells or as ultrafiltration cells in water purification and desalination system for separating potable water from sea or saline water, and also in laboratory systems for separating various types of permeates from feed solutions.
In recent years, a number of portable types of artificial kidneys including reverse osmosis cells have been proposed for removing toxic substances from body fluids, see for example U.S. Pat. Nos. 3,579,441 and 3,799,873. The cells used in such artificial kidneys involve parallel flow of the feed solution through the membranes of the cell. However, portable artificial kidneys require high recovery (percentage of feed obtained as membrane permeate), and low energy drive pumps, and therefore provide an extremely low volume flow. Cells having parallel flow of the feed solution with low volume flow rates tend to produce strong polarization, and even stagnation, causing the overall efficiency of the artificial kidney to be substantially decreased.
An object of the present invention is to provide a membrane separation cell having a relatively high linear flow rate with a relatively low volume flow rate, which permits the use of small pumps and thereby makes the cell particularly useful in portable artificial kidneys.
Another object of the invention is to provide a membrane separation cell which is capable of being miniaturized so as to provide a relatively small volume and low weight, a relatively large membrane area, a relatively high recovery, and a relatively low energy consumption.